GEC and Genelex are both brand names from England's MO Valve, Ltd. (Marconi-Osram). The Genelex boxed tubes we got when we bought the assets of a tug-boat company's electronic shop. The GEC tubes we stocked ourselves for marine radar
work. We bought them initially from RF Gain, then later, Richardson. The tubes are labeled with a sticker that quickly dis-colors when operated. They used both a year-week and a 2 letter date coding system.
The M-O company was born in the mid 1800's as the English branch of Siemens operating under that name. Through several purchases, mergers and name changes they are now known as GEC and have no tie-in other than historical to Siemens.

Osram was also part of the Marconi-Osram family. As shown on the example to the right, they were also known as the General Electric Co. of England (GEC). Not only was Marconi-Osram one of the first major manufacturers of tubes (Valves in England), they were also very heavily into lamps and light bulbs. An area where the Osram name is now teamed with Sylvania (Sylvania-Osram).